That led to a tense standoff. In a tussle with officers, one protester threw several bamboo sticks at police.

The culprit, who appeared to be staggering drunk, was berated by his fellow protesters. An angry crowd of protesters stood on the sidewalk at First and Main, berating the officers.

"Who the hell do you work for!?" one man shouted.

The tensions eased by about 6 a.m., as the streets reopened and police withdrew.

It remained unclear when the LAPD would move to clear the camp.

LAPD Commander Andrew Smith said that officers would "keep an eye on it throughout the day."

"We will continue to ask people to leave," he said. If they don't, he said police will "eventually" have to arrest people to clear the camp.

Four people were arrested early Monday for failure to disperse, Smith said.

Until the incident with the bamboo, there had been no acts of violence.

The tussle over the intersection was not in the Occupy organizers' plans. The protesters mostly stayed within the park until about 11:45 p.m., when a large truck with giant speakers pulled up along First Street, blasting Marvin Gaye's "What's Goin' On?" That brought a large crowd into the street, and having taken the street, most of the protesters saw no reason to give it up.

Smith teamed up with organizers to try to encourage the protesters to return to the park. "If they want to be arrested, we can certainly accommodate that," he said.

In the center of the plaza, a couple dozen protesters sat in concentric circles with arms linked -- apparently intending to be arrested.

About a third of the tents had been taken down on Sunday night, and more protesters were packing up as the deadline approached. But others were digging in.

Chad Knutsen, 22, built a tree fort out of pallets and twine. He used a cluster of four palm trees near the south steps of City Hall.

"The idea is to make it incredibly difficult to get us out," Knutsen said.

[Update at 10:46 a.m.]: A representative of the Occupy movement just filed suit in federal court seeking an injunction that would prevent the city and LAPD from evicting the City Hall encampment, KNX 1070 Newsradio reports.